This invention relates to an electromagnetic rotary actuator and, more particularly, to such an actuator which is simple in construction and can be used in a non-feedback mode.
Electromagnetically operated positioning actuators of various types are known in the prior art. An illustrative actuator of simple construction and effective operation is the linear motor disclosed in U.S. Pat. No. 4,016,441. This linear motor comprises a frame having an internal central pole piece spaced intermediate two permanent magnets which are attached to the frame. The central pole piece provides a support for a moveable coil member integrally formed with connecting arms pivotally fastened to an actuator arm carried on a pivoted potentiometer shaft. Such an actuator requires feedback circuitry for accurate positioning and the circuitry adds additional expense to the cost of the actuator.
It is therefore an object of the present invention to provide an actuator which does not require feedback circuitry for the accurate positioning thereof.
An illustrative actuator which may be operated without feedback circuitry is the electromechanical disc adder mechanism described in U.S. Pat. No. 3,812,729. This disc adder mechanism comprises a plurality of discs which are arranged co-axially on a drive shaft including discs keyed to the drive shaft and freely journalled discs frictionally coupled to turn with the keyed discs. Axial cam segments on adjacent keyed and freely journalled discs may be selectively brought into engagement by electromagnetically influenced stop means for changing the angular orientation of the freely journalled discs relative to the keyed discs, thus selectively to regulate the total axial dimension of the stack of discs on the shaft which is the output of the adder mechanism. While not requiring feedback circuitry for accurate positioning, the construction of the disc adder mechanism is relatively complex.
It is therefore another object of the present invention to provide an actuator of simple construction.